I have realised that I often talk about my work using UV (Ultraviolet) cameras on this blog but I have never properly explained how they work and why we specifically use them! So here I go.

Monitoring volcanic gas release is one of the major things volcanologists can do to aid with eruption forecasting (see this recent post by James Hickey to understand why we call it forecasting). A number of techniques have therefore been developed and used to measure the release of volcanic gases from volcanoes. One of such techniques is the UV camera (Bluth et al. 2007; Mori and Burton, 2006), pictured on the right. These were developed to solve the time and spatial issues with previous techniques (e.g., DOAS and COSPEC). These previous techniques required building up a plume profile using a stepper motor to scan across a plume or traversing under it. Traversing could be conducted on foot, by moped, by car, or aircraft! The UV camera immediately solves this problem as it essentially works like a conventional camera by taking still images using the UV part of the electromagnetic spectrum, instead of visible light like your everyday camera.

The UV camera and previous techniques all work on the principle of absorption of UV light by the volcanic gas sulphur dioxide (SO2). We specifically use SO2 due to the very low atmospheric background concentration of this gas. This makes it very easy to resolve the volcanic component. We can then, using two different cameras taking images at exactly the same time, compare two images (captured at the same time from each camera) where SO2 does and doesn't absorb (310 and 330 nm respectively). The graphic below illustrates the basic concept.

Graphic demonstrating the principle of ultraviolet spectroscopy. Incoming solar radiation (sunlight) is absorbed by sulphur dioxide within the volcanic plume. Light which isn't absorbed continues to the ultraviolet camera where the light intensity is recorded.

The plume from the NEC at Mt. Etna. Lines (a) and (b) indicate locations used to calculate plume transport speed.

We can then use the Lambert-Beer law to combine the images captured at each wavelength to work out the strength of absorption in each pixel. At this stage the calculated value will preserve real fluctuations in concentration but we won't know exact SO2 values without calibration! There are two distinct ways of doing this.

The first method is to image quartz gas cells, with known concentrations of SO2, with both cameras. We can then use the Lambert-Beer law again to combine the images at the separate wavelengths (310 and 330 nm - where SO2 does and doesn't absorb), which will create a series of new images with the absorption strength in each pixel - but this time we know exactly how much gas should be in front of the image - we can therefore use this to create what we call a calibration curve (or line) to map the values in the image of the volcanic plume to real SO2 concentrations.

The second method is to combine the DOAS method (Differential Optical Absorption Spectroscopy) with the UV camera images. DOAS works in a different way, essentially measuring a single pixel in the plume, and it has the ability to determine actual SO2 concentration (based on the absorption structure of SO2 at different wavelengths). During acquisition the concentration of SO2 will change at the location the DOAS is pointing, again enabling us to calibrate our images through comparison of the absorption pixel values in the UV camera images for the same pixel with the known value. Both of these processes are illustrated in the photo slideshow below. We can then calculate the rate at which SO2 is released from a specific crater, vent or fumarole by multiplying the plume speed by the total concentration of SO2 contained along a single line (e.g., line [a] in the image above), what we call the integrated column amount. Plume speed can be determined in a couple ways, including: optical flow algorithms which map the movement of pixels from image to image (e.g., Peters et al. 2015) or by using a cross-correlation technique (e.g., McGonigle et al. 2005) which uses the structure of the gas plume and how long it takes for parts of the plume to move from one point to another (illustrated in picture of plume from Etna above as lines [a] and [b]).

So this how we make UV camera measurements! The frequency that images can be taken is generally every 1 second but this can potentially be increased to 15 or even 30. This has the obvious benefit of being able to measure rapidly changing volcanic gas emissions associated with explosive activity such as strombolian volcanism or during passive activity (the constant quiescent release of gas). We can also begin to compare SO2 flux measurements with other datasets collected at similar time frequencies (e.g., Burton et al. 2015 offer an overview of UV camera studies). The benefits offered with an increase in spatial resolution can allow us to image more than one source at the same time - perfect where more than one crater (e.g., Etna) may be emitting gases or we may be observing a number of fumaroles (e.g., Vulcano).

Three days of fieldwork have passed since my last post, and what a mixed few days it has been. Sunday morning we got up to our previous measurement location on the flanks and the photo on the right was our view...not ideal measurement conditions for measuring a plume...especially if you can't see it! When faced with conditions like this in the field there are two options; either stick it out and see if conditions clear up or give up and clamber back down the mountain. This is the inspiration for my mildly creative blog title, it being the third post in my fieldwork series, as so far everything has gone well. That being said, we waited for three hours in the cold, wet and windy conditions till eventually the clouds cleared and we had a perfect(ish) view of the summit. Patience paid off!

Very small ashy emissions from the New South East Crater.

Fieldwork on Monday brought back memories from a field-trip to Etna I took during my Masters course at Lancaster University. We needed a new spot to measure from because of a different plume direction. When remote sensing a volcanic plume it is best if the plume isn't grounding, which unfortunately it has been doing a lot of recently. We decided to try a new spot on the edge of the Valle del Bove, a quite familiar 3 km walk undertaken during the Masters field trip which ends in a stunning view of one of the most impressive features on Etna (see images below). It also happened to have a decent view of the degassing craters with the plume appearing to drift towards Rifugio Sapienza.

Apparently we missed a few ashy explosions on the Saturday from the New South East Crater, never mind, because we saw a couple during fieldwork on Tuesday, but they were quite minor (see image on the right). The arrival of colleagues from Palermo, with a 4 by 4 panda suitable of travelling to Pizzi Deneri provided an ideal location for remote sensing, and significantly less mileage by foot!

One more day of work tomorrow, before the trip back to Palermo in our own faithful Fiat Panda.

Rarely, rarely, rarely in a campaign do you get excellent data on the very first day you set out to make measurements. Today was one of those days. We set out with a goal to compare two different Ultra Violet (UV) camera systems, and on the first day it appears we have got the data to do this successfully. Although it is always good to gather more just to be sure!

We were up early in the morning at 6 am to drive to Piano Provenzana for a short 30 minute walk to a good vantage point of the North East Crater (NEC) of Etna. See picture on the right. A familiar crater which has featured on my blog before and has provided a location for some previously published work. The NEC is often chosen as a location for UV work due to the high amounts of Sulphur Dioxide it emits daily. In the summer it is also easily accessible has much more reliable weather than other nearby sources such as Stromboli. There is also the added benefit of good food, wine, and sun.

Below are a selection of pictures which I took during the day and my attempt at imaging some clouds over the summit of Etna last night. Unfortunately tomorrow it looks like a rainy and cloudy day on the summit, so it looks like it may be a day of data processing instead.

It has been two years since my last visit to Sicily, and that is definitely too many. This year is a little bit different. It is the first time I head off to do research not directly related to my own PhD with the specific purpose of helping a first year PhD student (Tom Wilkes) with an exciting new gas remote sensing project.

A late flight in to Palermo meant a stay at a B&B in nearby Terrasini. I must admit that I had no idea what this area was like at all, so a bit of a gamble. But the gamble paid off, that is, once we had navigated all the many one way systems which were incorrectly labelled on Google Maps. A short walk from our B&B and there is a square filled with different options for food and drink. A late dinner and then back to the B&B ready for the morning journey to Palermo to pick up equipment for the journey to Linguaglossa.

The journey from Palermo to Catania.

The driving is always an interesting experience. This is my third time driving in Italy, on the mainland around Naples/Sorrento and previously in Palermo. There is no acclimatising to the driving style. My ethos: expect anything to happen at anytime and that anyone may do it. For those who have done the UK hazard perception part of the driving test it is much akin to clicking the mouse constantly and furiously! That being said there is a certain enjoyment in driving under these more testing conditions. The journey from Palermo to Catania is fantastic, relatively empty roads through a semi-mountainous region, with amazing towns perched on hilly outcrops.

I write this post from a lovely B&B in Linguaglossa, after an awesome and Norma Pizza, with a nighttime view of Etna in the distance. I think I might try some night time photography then it's early to bed before an early start tomorrow.

The result to leave the EU will have come as a surprise to many. As an Early Career Scientist I was particularly hoping that the UK would vote to remain, and was resoundingly disappointed as I checked my phone at 4 am to see that the leave campaign were going to clinch it. I have worked hard over the past six years completing a Masters and PhD to get my feet on the bottom of a very competitive ladder. All of a sudden I saw this slipping away. How hard will it be for me to find a job in two years time? Will I have to abandon my desire for an academic career? Should I start looking now for alternatives? Over the weekend I have had time to contemplate, whilst I thoroughly disagree with the decision to leave the EU, I have come to the conclusion that it is much too soon to run into any rash decisions.

I have read a number of articles and the facts associated with the benefit of the EU to UK science are quite simple. The UK receives more from the EU in scientific funding than it pays in and has done very well out of being part of the EU. Freedom of movement for students, graduate students, post-docs and above within the EU allows EU individuals to travel and work within the majority of EU countries. UK science is strong and therefore is a commensurately strong draw for the most talented individuals from the EU. If you haven't yet seen this video by an EU Law Expert, Professor Dougan, then I urge you to, it is an eye opening, honest and factual account of what the UK gains from the EU (in general). He also gives his views on EU Immigration in this article.

​The uncertainties surrounding Brexit are significantly more complex. I could go through a number of possible avenues, however, the future relationship of the UK with the EU is a complete unknown. Herein lies the problem, there is no plan. As a result of this uncertainty, UK science faces a period of uncertainty. With access to funding, scientists have more money for research, with access to the free market job positions can be filled by the very best candidates in the UK and EU. However, this also provides UK citizens with ability to study and research abroad. Over the years this has led to the development of a fantastic multi-cultural and highly productive scientific community, which needs to be retained.

In my own research all of my papers have been published and supported with the help of EU partners (and some specific European Research Council grants), specifically in Italy, although EU money supporting the work was not sourced within the UK. What does this mean? On the face of it, nothing. We will continue to work with our European colleagues, it will just be a bit more expensive for us to work abroad! Volcanology in particular is an area which requires significant international collaboration. Often when discussing my job with others I get the reply "But there are no [active] volcanoes in Britain". The UK volcanology community will therefore continue to collaborate internationally, within and without of the EU, regardless of what happens to our relationship with the EU. It is just a question of how difficult that will become.

Until we know more on what the future relationship will be uncertainties will prevail over the next few years. I sincerely hope that this decision does not leave Early Career Scientists with a reduction in job prospects, not just in the UK, but throughout the EU. More than ever, we need to come together as a community, the decision has been made and we need to make it work for everyone.

This work combines a large number of ultra violet camera based observations of sulphur dioxide release during and following strombolian explosions (which is called a gas flux trace) and smaller degassing events not necessarily associated with ejectiles (i.e. any magma release). Within the paper these are referred to as Vent 1 and Vent 2 events respectively. The benefit of collecting such a large number of gas flux traces is that any trends present or common characteristics between differing events can be compared. This allowed six flux trace types to be identified based on the patterns in gas release following the initial impulsive event associated with a strombolian explosion or smaller degassing event.

Following on from this, building on the work of Tamburello et al. (2012) who noticed that gas flux traces from strombolian explosions contained a coda (a period of elevated flux before a return to background levels), we were able to approximately separate out the distribution of gas mass into the initial impulsive gas release and the resultant coda. This allowed us to determine that a large proportion of the entire event (i.e. the initial release of gas added to the coda) could be contained within the coda - quite an interesting observation!

Alongside this work we performed a number of computational fluid dynamics simulations (using Ansys Fluent) of gas slug flow (Taylor bubble - see previous post). Over a range of parameters for the magma density, viscosity, and the conduit diameter we discovered that it was possible for the simulated gas slugs to shed gas bubbles, called "daughter bubbles", from the base of the slug at varying rates of efficiency. If these slugs were to rise over extended distances (simulations in the manuscript were over short distances in comparison to a full volcanic conduit) then significant mass could be lost from the slug into a daughter bubble train and contribute to the observed gas coda. There are of course other possibilities for the coda generation, however, daughter bubble could certainly play a role in determining how explosive an event may become and has wider implications for activity at other volcanoes.

This is the first study to combine gas flux measurements with computational fluid dynamics models. For full details you will of course have to read the paper! Associated videos are also available.

Last night I gave my Pint of Science talk in Sheffield and hopefully those who came learnt a thing or two about bubbles and their role in driving volcanic eruptions! My talk gave an overview of the range of activities that I study, from passive degassing through to lava fountaining, with a major focus on strombolian eruptions. In particular I discussed the role of volcanic gas slugs in generating such eruptions and some of the features which we have discovered during the course of my research at the University of Sheffield, including: past work at Etna which provided the first potential evidence for coalescence of gas slugs during volcanic activity, recent work just published in Geophysical Research Letters on the combination of gas measurements with computational models which demonstrated the possibility of daughter bubble production (the release of gas bubbles from the base of a slug) and that this could essentially cause slugs to destroy themselves (I will blog on this work soon), finally I introduced work I presented at AGU in 2014 which we are currently writing up for publication on laboratory and computational experiments conducted into multiple slug flow.

The journey of Bob the Bubble proved to be a popular addition to my talk, raising a few chuckles (video below). Bob the Bubble illustrates the journey of a gas bubble from a magma chamber, through a conduit and the shape (morphology) transitions which may occur throughout ascent. As part of my talk I also performed a few short demonstration experiments (see photo) on the coalescence of smaller bubbles to make a cap bubble, through to an ascending slug. With the kind assistance of Tom Wilkes we even managed to demo a series of slug coalescence events which worked perfectly on the first try. This was rather fortuitous as it didn't really work during testing on the previous day!

Dr Ed Daw of LIGO heritage spoke after my talk and gave some fascinating insights into the science and what it really took to detect gravity waves! He also hinted that further discoveries may be coming soon...

A very enjoyable event which it was a pleasure to be a part of. A big up to all the volunteers who made this event happen in Sheffield!

A variety of bubble shapes which may be found within magmas. Taken from my thesis: Pering, 2015.

Over the past 3 years I have delved into a large variety of topics in varying arrays of detail. However, a major theme throughout my work has been the investigation into the fluid dynamics of bubbles, and in particular a feature known as a Taylor bubble (or gas slug) e.g.Wallis (1969) and Bendiksen, (1985). Increasing mass and/or volume of a bubble its shape will naturally change, from a spherical bubble (Wegener and Parlange, 1973) to one that may elongate or deform, through to a cap bubble and then the Taylor bubble. The Figure on the right hand side illustrates this nicely. One of the major activities driven by the Taylor bubble is strombolian volcanism, be it that related to single events (as at Stromboli) or more rapid events, as I have previously observed at Etna.

The Taylor bubble has a number of predictable parameters, including: the distances between the wall and the Taylor bubble edge (termed the falling film), the rise speed of the base of the Taylor bubble, and certain lengths associated with the passage of the bubble - the wake and interaction lengths (Campos and Guedes de Carvalho, 1988). In addition there are a number of dimensionless numbers which help characterise the behaviour of a gas bubble within a fluid, e.g. Reynolds, Morton, Eotvos, and Weber numbers. Within volcanology one area of focus is on the determination of the masses of these Taylor bubbles (i.e. using ultra-violet cameras), which can then be used to work out final lengths and possible burst pressures of the bubbles.

All of these parameters above require a set of distinct equations to calculate, which, can sometimes be difficult to locate. There are very few (in fact I didn't find any) resources available online for the calculation of many of these parameters and their calculation often involves the loading up of software such as Matlab. It is for these reasons that I have created an online calculator to enable the calculation of a range of useful (to me and hopefully to others!) dimensionless numbers and Taylor bubble related features. This resource is available here, and for the moment I have called it the "Slug Calculator". It is currently split into two sections. The first "Dimensionless Numbers and Taylor Bubble Parameters" essentially allows the calculation of parameters related to the section title, while the second "Taylor Bubble Mass and Length Inputs/Results" uses pressure, temperature, mass and ratio values (of the common volcanic gases) to estimate a variety of potentially important Taylor Bubble parameters.

The calculator is a work in progress, so will be improved and altered as I notice errors or learn how to make improvements!

This year Pint of Science is coming to Sheffield. ​I will be in esteemed company with Dr Ed Daw who will be talking about gravitational waves detected as part of the LIGO experiment in a combined event called Ripples and Bangs. I will of course be contributing the "Bangs" part of the event - where I will discuss my previous, ongoing and future research into the behaviour of bubbles at basaltic volcanoes.

Volcanic eruptions are one of the most spectacular phenomena we see on this planet. Through the medium of beer, I will explain the journey of the gas bubbles which drive these eruptions, from birth, to eruption at the surface. I will explore how we investigate these bubbles, by using state-of-the-art monitoring equipment to measure gas output and computer models to simulate gas flow. Fully unlocking the secrets of this journey is an essential future goal in volcanology, where any progress made will play a key part in aiding eruption forecasting.

This is a ticketed event on the 25th May 2016 in Bloo 88, tickets are available for purchase here.

As those will have ever attended EGU will testify - it is very very expensive. This year, I was only partially funded by my department (many thanks to them for the money that was provided!), so I tried in earnest to keep costs down. So here are a number of hopefully helpful tips:

Plan ahead and well in advance where possible - this is something I failed miserably on. This will allow you to take advantage of low cost flights with EasyJet (from the UK) and also to pay the reduced fee for conference registration.

If possible go with friends/colleagues from your department, this will help cut costs down looking for accommodation or enable a large group to share a flat from AirBnB.

The conference has plenty of free water and tea/coffee. The water is dotted around everywhere. The coffee and tea can sometimes take a bit of hunting down. Good places to look are the main poster halls during the allocated break periods.

Use the Early Career Scientists Lounge. They have assorted drinks and fruit. Although, everything seems to run about by early morning.

Attend your sections meeting - if you get their early enough you can get free lunch. It's also a good insight into what it takes to run a section.

Don't be afraid to go off the beaten track for food - eating in the city centre is generally quite expensive.

Transport:

Not much to be done here, free travel in the city during the days of the conference (Monday to Friday).

So how did I fair? Cheaper than previous years, mainly because I only attended two days of the conference. I managed to cut my accommodation costs in half (on a per day basis).